function checkedThis(obj){
    var boxArray = document.getElementsByName('ans_id_arr[]');
    for(var i=0;i<=boxArray.length-1;i++){
        if(boxArray[i]==obj && obj.checked){
            boxArray[i].checked = true;
        }else{
            boxArray[i].checked = false;
        }
    }
}
function  checkTrue(obj) {
    var boxArray = document.getElementsByName('ans_id_arr[]');
    for(var i=0;i<=boxArray.length-1;i++){
            boxArray[i].checked = true;
    }
}